1. Field of the Invention
The present invention relates to a mobile terminal that may reduce a specific absorption rate, and more particularly, to a mobile terminal that may reduce a specific absorption rate and includes an antenna pattern and a ground pattern.
2. Discussion of the Background
Due to the rapid development of communication technology using mobile terminals, the mobile terminal has become popular. Accordingly, the average time spent using a mobile terminal has rapidly increased. Therefore, concern about whether electromagnetic waves radiated from the mobile terminal have a harmful influence on a human body has increased.
A Specific Absorption Rate (SAR) is generally used as a numerical value for indicating the degree of harmful influence on a human body caused by electromagnetic waves radiated from the mobile terminal. The SAR is the electric power absorbed per unit mass of a human body cell, measured in units of W/kg. The SAR of a human body is measured using a device called a human body phantom, which has an electric constant similar to human body tissue, because it is difficult to directly measure a human body. The SAR is represented by the following equation:
  SAR  =            1      2        ⁢          (              σ        ρ            )        ⁢                          Ei                    2      where σ is the conductivity of a human body phantom, ρ is density, and |Ei|2 is the peak value of a local electric field vector.
The SAR in human body tissue is proportional to the square of electric field strength within the tissue and is determined by parameters of the incident electromagnetic field, such as the frequency, strength, direction, and source of an electromagnetic field, the relative position of a target object, genetic properties of a characteristic tissue of an exposed human body, and the ground effect and exposed environment effect.
Several countries have established and regulate safety standards regarding human body exposure to electromagnetic waves based on the SAR. In order to satisfy SAR standards, various methods of reducing the SAR may be used when manufacturing a mobile terminal.
One such method is to coat Electro Magnetic Interference (EMI) paints on the mobile terminal's case. The EMI paints provide an electromagnetic shielding effect by electromagnetically separating the opposite sides of a closed curved surface of a metal body. When EMI paints are coated on the mobile terminal's case, electromagnetic waves generated within the case may not radiate from the mobile terminal. It may also prevent the generation of static electricity and electrification. While this method has an influence on the EMI and electromagnetic susceptibility (EMS) of a terminal, it does not fundamentally decrease the influence of electromagnetic waves radiated from the antenna. Further, in theory, when EMI paints are coated on the mobile terminal, the SAR to the human body may increase by re-reflection generated due to EMI paints.
Another method is to arrange various parts within the mobile terminal in consideration of the SAR. However, re-arrangement of various parts within the mobile terminal in order to reduce the SAR may negatively affect communication quality and/or the external shape of the mobile terminal.